444 PHYSIOLOGY. 



of insects be considered the analogues of the anterior limbs ; but I 

 prefer considering them as the posterior limbs, and, indeed, because 

 those are the least perfect, not only in structure, but also in function. 

 Where, therefore, true limbs first present themselves, there must they 

 be considered as the inferior ones or legs. Both, however, the arm and 

 the leg differ from each other in the angles of their joints, being opposed 

 so that the angle which in the anterior extremities open outwards, on 

 the posterior ones open posteriorly. But these differences are not found 

 in the extremities of insects; the anterior ones are merely distinguished 

 from the posterior ones by their situation, for their corresponding angles 

 all open upon one side. Hence, therefore, the hip is not the thigh, but 

 the hip, and the trochanter and femur form conjunctively the thigh. 

 The hip is the head of the femur, the trochanter its neck, and the femur 

 its tubular body. This division of the femur into three parts is occa- 

 sioned by the feet being in insects so placed, that they proceed as it 

 were from the lower end, and direct themselves upAvards, in which 

 direction they possess considerable power of motion, which was only to 

 be attained by this mode of articulation. If in solitary cases more 

 mobility is required, the trochanter must be divided into several pieces, 

 and this is exemplified in the genus Pimpla ( 83. 2.). If, however, 

 it be the elbow or olecranon, in this instance we must adopt the exist- 

 ence of two successive patellae, for which there is no analogy ; but if a 

 division of the thigh into three parts may be imagined, it is still more 

 possible to conceive its subdivision into four. If now the coxa, 

 trochanter, and femur be the subdivided superior thigh (femur), the 

 tibia must necessarily be the lower thigh (tibia). The angles of both 

 joints fully harmonise with this view, in as far as they always open 

 either posteriorly or inferiorly. The first large joint of the tarsus then 

 indicates the metatarsus, as the basal bones are wanting, and the 

 following are then the phalanges. They vary considerably in number; 

 sometimes they are entirely wanting, but never more than four exist. 



If after this explanation, which must still appear forced, from the 

 deficiency of the basal bones of the foot, we look around us for an 

 analogy in the higher animals, we find the most perfect conformity in 

 the structure of the foot in birds. In these, also, the basal bones of 

 the foot are deficient, and in them, also, there is a variation in the 

 number (from one to four) of their phalanges. This variation is found 

 in every individual bird, in as far as each of its four toes, commencing 

 inwardly, increase one joint, so that the innermost, generally the 



